1. Field of the Invention
The present invention relates to an underframe constituting of rolling stock or a railway vehicle body, and particularly it relates to an underframe construction of a vehicle which is suitable for vehicles provided with underfloor equipment. It will be understood that when this specification refers to a "vehicle", railway rolling stock is contemplated.
2. Description of the Prior Art
An underframe in a conventional vehicle is shown, for example, in "Rolling Stock Technology No. 159" issued by Japan Association of Rolling Stock Industry, in September, 1982, at page 29. In the construction of this example, a corrugated plate is used for a floor panel, a board material for the external boards of a side framing and a roof framing, and shaped steel for the underframe and frames. A description will be made on this construction with reference to FIGS. 24 to 26. In these figures, numeral 1 denotes an underframe, 2 a side sill disposed on both sides of said underframe 1, and 3 a cross beam arranged so that it connects the end portions of said side sills 2. Numeral 4 denotes a corrugated plates provided on the top side of the aforesaid cross beams 3. Moreover, numeral 5 denotes a body bolster arranged at positions at which the vertical load on the aforesaid underframe 1 is supported, and which correspond to the location of trucks 6 an end sill provided so that it connects the ends of the side sills 2, and 7 a center sill by which a vehicle-end compression load applied on the end portions of the underframe 1 is transmitted to the aforesaid end sills 6.
In such a construction, the load of passengers and the weight of various equipment and fittings inside a vehicle act on the floor of the underframe 1 from above, while the weight of various electric apparatuses etc. acts on the floor from below, and these weights are borne mostly by the cross beams 3. Accordingly, the cross beams 3 are arranged generally at intervals of 500 mm to 700 mm in the longitudinal direction of the body of the vehicle. Moreover, each of said cross beams 3 is formed to have a -shaped cross section, as shown in FIG. 26, with an appropriate length in the vertical direction and an appropriate cross-sectional area so as to secure the rigidness and strength sufficient enough to bear said weights safely. Consequently, the weight of the cross beams 3 accounts for about 20% of the total weight of the underframe 1, which has been an impediment to weight reduction of the vehicle body. Furthermore, a space formed between the underframe 1 and rails is narrowed because of the large length in the vertical direction of said cross beams 3, and this narrows the space required for fitting the aforesaid various underfloor equipment. As a result, work is troublesome when varieties of underfloor equipment or ducts or the like are fitted in a large number to the underfloor part of the underframe 1. In addition, the overhead position of work required for fitting hinders working efficiency, while necessitating much labor. When it is necessary to provide heat insulating materials on the whole of the lower side of the underframe 1, said space is further reduced, thus causing disadvantages that it becomes difficult to secure the space required for the aforesaid underfloor equipment or the like and that there is a marked increase in labor, and the lower structure of the underframe becomes undesirably complex.